a. Field of the Invention
This invention relates to drive axles. In particular, the invention relates to a drive axle shaft that is both lightweight and capable of use in a semi-floating axle.
b. Background Art
Vehicle drive axle shafts are subjected to significant loads. The shafts transmit significant torque to the vehicle wheels and are subject to rapid starts and stops in operation. In semi-floating axles, the drive shafts also support a portion of the vehicle weight. Because of the significant loads imposed on the shafts, most shafts are formed of solid metal to provide sufficient rigidity and strength. Solid drive axle shafts, however, add significant weight to the vehicle. This weight has a negative effect on fuel economy and imposes additional loads on other vehicle components. Further, solid drive axle shafts incur significant material costs.
Because of the disadvantages associated with solid drive axle shafts, hollow drive axle shafts have been developed as shown, for example, in U.S. Pat. No. 5,213,250, the entire disclosure of which is incorporated herein by reference. Hollow shafts, however, generally cannot be used in semi-floating axles. In a typical semi-floating axle, the inboard end of the drive axle shaft is splined or keyed to a side gear of a vehicle differential. In order to prevent movement of the shaft in an outboard direction, a semi-circular retaining clip or “C-clip” is disposed on an inboard side of the side gear and disposed within a machined groove formed in the outer surface of the drive axle shaft. The dimensions of a hollow drive axle shaft (i.e., the distance between the outer and inner diameters of the shaft) generally make it difficult or impossible to machine the groove thereby limiting or preventing the use of hollow drive axle shafts in semi-floating axle applications.
The inventor herein has recognized a need for a drive axle shaft that will minimize and/or eliminate one or more of the above-identified deficiencies.